This invention relates to network communications. Many network implementations employ end-to-end management, in which a “head end” device supplies information to one or more recipients, usually called “clients.” Typically, the head end device is a computer, which acts as a server to one or more client devices, which also may be computers. In a typical broadcast network, communication between the head end and the clients is one-way, with the head end broadcasting the same information to all clients on the network.
In some circumstances, a client can open a point-to-point interactive channel with the head end, or the head end can open a point-to-point interactive channel with a client. The interactive communication may include alert management messages from the head end to the client, which generally represent the head end's response to an alert from the client or which may be a proactive action by the head end. An alert is a communication on an interactive channel opened by the client when the client detects a noteworthy condition and needs to inform the head end of the condition. An alert may be generated, for example, when a software or data download from the head end to a client fails a cyclical redundancy check (CRC). The head end typically reacts to an alert by performing the necessary operations and/or by sending an appropriate alert management message to the client on the interactive channel. In some cases, the interactive channel opened by the client closes before an alert management message can be sent, and the head end calls for a new interactive channel to relay the alert management message.
In some circumstances, the head end cannot open an interactive channel with a client. The head end may be physically unable to open an interactive channel, or the head end may be stopped from opening an interactive channel because of concerns related to cost, efficiency, or availability of resources. The client may be able to open an interactive channel with the head end, but the head end cannot compel the client to open the channel. When the head end lacks control to initiate an interactive channel with a client, the head end may not be able to pass alert management messages to the client by way of an interactive channel.